Means used to supply oxygen in culturing apparatus and bioreactors used for the culturing of cells, microorganisms and tissues include absorption from the surface of the culture solution, blowing in by means of a sparger, and aeration by means of agitation, etc. Furthermore, methods in which oxygen is supplied via a membrane have been described in Japanese Laid-Open Patent Application (Koaki) No. 57-159535, Japanese Laid-Open Patent Application (Kokai) No. 59-175877, Japanese Laid-Open Patent Application (Kokai) No. 60234580 and Japanese Laid-Open Patent Application (Kokai) No. 61-100190, etc.
Furthermore, in Bunri Gijutsu, Separation Technology, Vol. 14, No. 4 (1984), a method is introduced in which the efficiency of acetic acid fermentation is increased by fixing acetic acid bacteria (which are aerobic bacteria) to the outside of a hydrophobic hollow membrane structure, and causing air to flow through said hollow membrane structure.
In the abovementioned conventional systems involving absorption from the surface of the culture solution, there are limits to the oxygen supply capacity, and this capacity is unavoidably insufficient in cases where the culture tank is large in size. In the case of blowing in by means of a sparger of aeration by agitation, there is a high possibility of bubble or agitation damage in the case of delicate cells such as animal cells, etc., or cells which have little resistance to a shearing force.
The methods described in the aforementioned laid-open patent applications and Bunri Gijutsu, Separation Technology, which solve the abovementioned problems, supply O.sub.2 to a culture solution located on the outside of a semi-permeable membrane tube without generating any bubbles; this is accomplished by causing O.sub.2 to flow through the interior of said semi-permeable membrane tube. However, since this is a calm supply state which lacks the agitating action that accompanies the rise of bubbles generated in the culture solution, a bias tends to be generated in the concentration of solute oxygen in the culture solution inside the tank, so that the concentration of solute oxygen in the culture solution near the circumference of the semi-permeable membrane is constantly high in relative terms; accordingly, the supply efficiency is still insufficient, so that it is difficult to obtain desirable results using such a method, especially in the case of a large apparatus.